This invention relates to storage tanks, and more particularly to underground tanks for storing motor fuel, such as gasoline or diesel fuel.
Underground tanks and aboveground tanks used for storing petroleum and petrochemicals are normally designed to be leakage resistant to minimize loss of their contents in or onto the ground, which in excess amounts might contaminate the soil and pollute surrounding areas.
Over the years, a number of underground, above-ground, and transportation tanks have been developed for storing petroleum, petrochemicals, and other materials. Typifying these prior art storage tanks are those found in U.S. Pat. Nos. 2,758,747; 3,747,800; 4,230,061; 4,374,478; and 4,408,628. These prior art tanks have met with varying degrees of success.
In recent years, many states, such as New York, Florida, and California, have enacted secondary containment laws or regulations to further protect the environmental quality of the land and surrounding area on which the tanks are located. Secondary containment laws and regulations generally require operators or owners of tanks storing petroleum, chemicals, or hazardous material, to provide a secondary containment vessel, such as an exterior shell or a leak-proof housing, which would surround the tank and serve as a backup safety vessel to contain any materials which might leak out of the primary tank.
In an effort to comply with these secondary containment laws and regulations, some operators and owners of underground storage tanks have encased their existing underground tanks (usually steel tanks) with concrete. Others have placed an exterior liner or flexible bag around their underground tanks and backfilled. Both of these techniques require excavation of the tank sites, and replacement or reinstallation of the tanks, along with additional construction. These prior art secondary containment techniques are expensive, time-consuming, cumbersome, and often unreliable.
It is, therefore, desirable to provide an improved underground tank facility which complies with secondary containment regulations and overcomes most, if not all, of the above problems.